(begin (write-char #\a) (flush-output-port (current-output-port)) (exit))
=> a
(begin (write-char #\a) (close-output-port (current-output-port)) (exit))
=> a
(begin (write-char #\H) (write-char #\e) (write-char #\l) (write-char #\l) (write-char #\o) (write-char #\space) (flush-output-port) (write-char #\W) (write-char #\o) (write-char #\r) (write-char #\l) (write-char #\d) (write-char #\!) (flush-output-port (current-output-port)) (exit))
=> "Hello World!"